Treatment method and treatment device for Lyocell fiber production wastewater

Abstract

The invention provides a treatment method and a treatment device for lyocell fiber production wastewater. According to the treatment method, by adopting an advanced pretreatment technology and screening proper process parameters, after wastewater components are subjected to ring opening and chain scission through physical and chemical reactions, the biodegradability of the wastewater is improved, the salinity of the wastewater is reduced, the water quality reaches the environmental conditions suitable for growth of microorganisms, and then subsequent biochemical treatment and deep treatment are utilized to achieve the purpose of improving the biodegradability of the wastewater. The wastewater index is higher than the national standard first-level A direct discharge standard, the treated discharged wastewater can be further recycled by 30%, water waste is avoided, water resources are saved, the aims of saving cost, reducing input cost and paying attention to product quality are met for producers, and the Lyocell fiber sewage treatment technology has wide application and popularization value as a more professional Lyocell fiber sewage treatment technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of viscose fiber production, and particularly relates to a treatment method and device for Lyocell fiber production wastewater. BACKGROUND

[0003] Mixed wastewater produced in Lyocell fiber production contains cellulose, N-methyl morpholine N-oxide (NMMO) and inorganic salts, etc. At present, most of the viscose Lyocell fiber production mixed wastewater treatment in China adopts a high-level oxidation technology to be discharged to a biochemical process for further treatment, but this technology has a high operation cost and will produce solid waste, which is easy to cause secondary pollution. At the same time, the Lyocell wastewater discharge standards of enterprises producing new solvent method cellulose fiber in China are discharged according to the chemical fiber enterprise standard, and the best can only be discharged according to the national standard level B standard, and there is no technology and process flow to realize the national standard level A direct discharge standard. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a treatment method for Lyocell fiber production wastewater. The treatment method realizes that the wastewater index is higher than the national standard level A direct discharge standard, and the treated and discharged wastewater can be further recycled by 30%.

[0005] To achieve this purpose, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a treatment method for Lyocell fiber production wastewater, comprising:

[0007] S1: high-level oxidation pretreatment: mixing and reacting acidic wastewater and alkaline wastewater produced in Lyocell fiber production to obtain first mixed wastewater, controlling the pH of the first mixed wastewater to be 9-10, performing air floatation treatment to obtain air floatation effluent; mixing the acidic wastewater and the air floatation effluent to obtain second mixed wastewater, controlling the pH of the second mixed wastewater to be 2.8-3; performing iron-carbon micro-electrolysis treatment on the second mixed wastewater, controlling the pH of the micro-electrolysis effluent to be 4-4.5; performing Fenton oxidation treatment to obtain Fenton oxidation effluent, mixing the Fenton oxidation effluent with the alkaline wastewater to obtain third mixed wastewater, controlling the pH of the third mixed wastewater to be 7.5-9.0; performing coagulation treatment and first flocculation treatment to obtain first flocculation effluent;

[0008] S2: biochemical treatment: sequentially performing EGSB anaerobic biochemical treatment and two-stage A / O biochemical treatment on the first flocculation effluent to obtain A / O biochemical effluent;

[0009] S3: deep treatment: the A / O biochemical effluent is sequentially subjected to second flocculation treatment, BAF treatment and ozone treatment to obtain ozone effluent, thereby obtaining clean water.

[0010] Preferably, the air floatation treatment is performed using 5-8wt% PAC and 1-5wt% PAM.

[0011] Preferably, the ratio of the water inflow, the PAC inflow and the PAM inflow in the air floatation treatment is 120m 3 / h:(800-1000)L / h:(100-200)L / h.

[0012] Preferably, the dissolved gas pressure in the air floatation treatment is 0.56-0.6Mpa; and the treatment time is 1-5h.

[0013] Preferably, the time for the iron-carbon micro-electrolysis treatment is 4-8h.

[0014] Preferably, the Fenton oxidation treatment is performed using 10-15wt% ferrous sulfate solution and 27-35wt% hydrogen peroxide for 2-6h.

[0015] Preferably, the ratio of the water inflow, the ferrous sulfate solution inflow and the hydrogen peroxide inflow in the Fenton oxidation treatment is 30m 3 / h:(1000-1500)L / h:(500-1000)L / h.

[0016] Preferably, the coagulation treatment uses 10-15wt% PAC.

[0017] Preferably, the first flocculation treatment uses 1-5wt% PAM.

[0018] Preferably, the ratio of the water inflow, the PAC inflow and the PAM inflow in the coagulation treatment is 30m 3 / h:(800-1000)L / h:(100-200)L / h.

[0019] Preferably, the residence time of the EGSB anaerobic biochemical treatment is 1-7 days.

[0020] Preferably, the residence time of the two-stage A / O biochemical treatment is 1-7 days.

[0021] Preferably, the concentration of ozone in the ozone treatment is 100-200mg / L, and the air inflow is 200-400Nm 3 / h.

[0022] Preferably, the time for the ozone treatment is 2-5h.

[0023] Preferably, after the clean water is obtained, the clean water is sequentially subjected to magnetic coagulation and activated carbon adsorption treatment, and the effluent is recycled.

[0024] In a second aspect, the present application provides a device for treating lyocell fiber production wastewater, comprising:

[0025] a high-level oxidation pretreatment unit, a biochemical treatment unit and a deep treatment unit connected in sequence;

[0026] The high-level oxidation pretreatment unit comprises:

[0027] an acidic wastewater collection tank and an alkaline wastewater collection tank;

[0028] a mixed wastewater tank connected to the acidic wastewater collection tank and the alkaline wastewater collection tank;

[0029] a gas floatation device connected to the mixed wastewater tank;

[0030] an iron-carbon micro-electrolysis acidification tank connected to the gas floatation device and the acidic wastewater collection tank;

[0031] a Fenton oxidation system connected to the iron-carbon micro-electrolysis acidification tank;

[0032] a coagulation reaction tank connected to the Fenton oxidation system and the alkaline wastewater collection tank;

[0033] a first flocculation reaction tank connected to the coagulation reaction tank;

[0034] The biochemical treatment unit comprises:

[0035] an EGSB anaerobic biochemical system connected to the first flocculation reaction tank;

[0036] a two-stage A / O biochemical system connected to the EGSB anaerobic biochemical system;

[0037] The deep treatment unit comprises:

[0038] a second flocculation reaction tank connected to the two-stage A / O biochemical system;

[0039] a BAF biological filter connected to the second flocculation reaction tank;

[0040] an ozone contact tank connected to the BAF biological filter;

[0041] and a clean water tank connected to the ozone contact tank.

[0042] Preferably, the device further comprises a magnetic coagulation tank connected to the clean water tank, and an activated carbon adsorption tank connected to the magnetic coagulation tank.

[0043] Compared with the prior art, the present application has the following advantages:

[0044] The present application is aimed at the special properties of Lyocell fiber industrial wastewater, and a new planning of the water treatment process route is provided. The present application provides a treatment method for Lyocell fiber production wastewater. The method uses advanced oxidation technology to pretreat the Lyocell wastewater. By utilizing the properties of the wastewater, the acidic wastewater and the alkaline wastewater are modified to the reaction section required to adjust the pH of the advanced oxidation reaction. The self-generated wastewater properties are fully utilized for reagent addition, which saves the amount of external acid and base. At the same time, the pretreatment process improves the biodegradability of the wastewater (original B / C < 0.1, treated B / C ≥ 0.45). By using advanced pretreatment technology, the pH of each effluent section is selected within a suitable range, so that after the wastewater components are subjected to physical and chemical reactions to open the ring and break the chain to improve the biodegradability of the wastewater, and the salt content of the wastewater is reduced, the water quality meets the environmental conditions suitable for the growth of microorganisms. Then, through subsequent biochemical treatment and advanced treatment, the wastewater indicators are higher than the national standard A direct discharge standard, and the treated effluent wastewater can be further recycled by 30%, avoiding water waste and saving water resources. The present application meets the goals of cost saving, reduced input cost and focus on product quality for the producer, and has wide application value as a more professional Lyocell fiber wastewater treatment technology. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0046] According to the analysis of the composition of Lyocell wastewater, the composition of Lyocell fiber wastewater is complex, and the dissolved fiber, NMMO solvent and high molecular organic additives are difficult to degrade in the wastewater treatment process. In addition, according to the analysis of the test data of Lyocell wastewater, the acid pH of high-concentration acid and alkali wastewater is 12.0, the acid and alkali are strong, the COD is >15000, the TN is >3000, the pollutant content is high, the biodegradability is poor, and the salt content of high-concentration wastewater and pure water membrane concentrated water is >10000.

[0047] Therefore, the present application provides a treatment method for Lyocell fiber production wastewater, which comprises:

[0048] S1: advanced oxidation pretreatment: the acid wastewater and the alkaline wastewater produced by lyocell fiber production are mixed and reacted to obtain first mixed wastewater, the pH of the first mixed wastewater is controlled to be 9-10, air flotation treatment is carried out to obtain air flotation effluent; the acid wastewater and the air flotation effluent are mixed to obtain second mixed wastewater, the pH of the second mixed wastewater is controlled to be 2.8-3; the second mixed wastewater is subjected to iron-carbon micro-electrolysis treatment, the pH of the micro-electrolysis effluent is controlled to be 4-4.5; Fenton oxidation treatment is carried out to obtain Fenton oxidation effluent, the Fenton oxidation effluent is mixed with the alkaline wastewater to obtain third mixed wastewater, the pH of the third mixed wastewater is controlled to be 7.5-9.0; coagulation treatment, first flocculation treatment are carried out to obtain first flocculation effluent;

[0049] S2: biochemical treatment: the first flocculation effluent is subjected to EGSB anaerobic biochemical treatment and two-stage A / O biochemical treatment in sequence to obtain A / O biochemical effluent;

[0050] S3: advanced treatment: the A / O biochemical effluent is subjected to second flocculation treatment, BAF treatment and ozone treatment in sequence to obtain ozone effluent, and clear water is obtained.

[0051] In the present application, for the wastewater produced by lyocell fiber production, first, the advanced pretreatment technology is adopted, and the appropriate process parameters are selected, so that the composition of the wastewater is opened and broken through physical and chemical reactions to improve the biodegradability of the wastewater, from the original B / C < 0.1 to B / C ≥ 0.45. The advanced oxidation pretreatment comprises: mixing and reacting the acid wastewater and the alkaline wastewater produced by lyocell fiber production to obtain first mixed wastewater, controlling the pH of the first mixed wastewater to be 9-10, preferably 9.2-9.5, and carrying out air flotation treatment to obtain air flotation effluent; mixing the acid wastewater and the air flotation effluent to obtain second mixed wastewater, controlling the pH of the second mixed wastewater to be 2.8-3, preferably 2.85-2.9, and carrying out iron-carbon micro-electrolysis treatment on the second mixed wastewater, controlling the pH of the micro-electrolysis effluent to be 4-4.5, preferably 4.1-4.3, and carrying out Fenton oxidation treatment to obtain Fenton oxidation effluent; mixing the Fenton oxidation effluent with the alkaline wastewater to obtain third mixed wastewater, controlling the pH of the third mixed wastewater to be 7.5-9.0, preferably 8.0-8.5, and sequentially carrying out coagulation treatment and first flocculation treatment.

[0052] In some embodiments of the present application, the acid wastewater and the alkaline wastewater are first mixed at a stable ratio, which can maintain the stability of the wastewater quality, and after the acid wastewater and the alkaline wastewater are completely reacted, the pH of the first mixed wastewater is controlled to be between 9 and 10. In some specific embodiments of the present application, the acid wastewater in the high-concentration acid wastewater collection tank is continuously sent into the high-concentration conditioning tank by a water pump, the inlet flow rate is 20 m 3 / h, and at the same time, the alkaline wastewater in the high-concentration alkaline wastewater collection tank is continuously sent into the high-concentration conditioning tank by a water pump, the inlet flow rate is 60 m3 The two kinds of high-concentration wastewater are mixed in a stable proportion to keep the quality of the wastewater stable. When the reaction of the acidic wastewater and the alkaline wastewater in the high-concentration adjusting tank is complete, the pH of the first mixed wastewater is controlled to be 9-10, and the first mixed wastewater is sent to the pressurized dissolved air flotation equipment for flotation treatment.

[0053] In some embodiments of the present application, the flotation treatment is performed using 5-8 wt% PAC and 1-5 wt% PAM, preferably using 5-6 wt% PAC and 1-3 wt% PAM, and more preferably using 5 wt% PAC and 1 wt% PAM. The ratio of the water inflow, the PAC inflow, and the PAM inflow in the flotation treatment is 120 m 3 / h:(800-1000) L / h:(100-200) L / h, preferably 120 m 3 / h:(800-950) L / h:(100-180) L / h, more preferably 120 m 3 / h:900 L / h:150 L / h. The dissolved air pressure in the flotation treatment is 0.56-0.6 MPa, preferably 0.58-0.59 MPa; and the treatment time is 1-5 h, preferably 1-2 h. In some specific embodiments of the present application, the wastewater from the high-concentration adjusting tank is continuously sent to the pressurized dissolved air flotation equipment using a water pump, with a water inflow of 120 m 3 / h, 5 wt% PAC is added to the dosing pipe mixer of the flotation water inflow pipeline at a flow rate of 900 L / h, and 1 wt% PAM is added to the pipeline mixer of the flotation water inflow at a flow rate of 150 L / h, and the dissolved air pressure is adjusted to be 0.56-0.6 MPa; the reaction residence time is 2 h, and the flotation effluent flows into the next stage.

[0054] In some embodiments of the present application, the acidic wastewater and the flotation effluent are mixed to obtain second mixed wastewater, and the pH of the second mixed wastewater is controlled to be 2.8-3, and the second mixed wastewater is subjected to iron-carbon micro-electrolysis treatment. In some specific embodiments of the present application, the acidic wastewater from the high-concentration acidic wastewater collection tank is pumped into the iron-carbon micro-electrolysis acidification tank using a water pump, with a flow rate of 7 m 3 / h, and the second mixed wastewater is mixed with the flotation effluent. At this time, the pH of the second mixed wastewater is about 2.8-3, and the second mixed wastewater flows into the iron-carbon micro-electrolysis reaction tank, with a residence time of 4-8 h, preferably 6 h; the iron-carbon micro-electrolysis acidification tank uses an aeration system to supplement aeration, and the aeration is controlled to generate a small amount of bubbles on the surface of the micro-electrolysis tank.

[0055] In some embodiments of the present application, the pH of the effluent of the iron-carbon micro-electrolysis treatment is controlled to be 4-4.5, and then the effluent is subjected to Fenton oxidation treatment to obtain Fenton oxidation effluent. The Fenton oxidation treatment is performed for 2-6 h using 10-15 wt% ferrous sulfate solution and 27-35 wt% hydrogen peroxide, preferably 10-13 wt% ferrous sulfate solution and 27-30 wt% hydrogen peroxide for 2-4 h, and more preferably 10 wt% ferrous sulfate solution and 27 wt% hydrogen peroxide for 3 h. The ratio of the flow rates of the influent, the ferrous sulfate solution and the hydrogen peroxide in the Fenton oxidation treatment is 30 m 3 / h:(1000-1300) L / h:(500-800) L / h, and more preferably 30 m 3 / h:(1000-1300) L / h:(500-800) L / h, and more preferably 30 m 3 / h:(1000-1300) L / h:(500-800) L / h, and more preferably 30 m

[0056] In the present application, after the Fenton oxidation treatment, the Fenton oxidation effluent is mixed with alkaline wastewater to obtain third mixed wastewater, the pH of the third mixed wastewater is controlled to be 7.5-9.0, and then coagulation treatment and first flocculation treatment are performed. The coagulation treatment is performed using 10-15 wt% PAC, and preferably 10-12 wt% PAC; the first flocculation treatment is performed using 1-5 wt% PAM, and preferably 1-3 wt% PAM.

[0057] In some embodiments of the present application, the effluent subjected to Fenton oxidation treatment is allowed to flow into the coagulation reaction tank, high-concentration alkaline wastewater is continuously pumped into the coagulation reaction tank to mix with the Fenton effluent, the opening degree of the regulating valve is controlled to make the pH of the coagulation reaction tank be between 7.5 and 9.0, 10% mass concentration PAC is added to the coagulation reaction tank at a flow rate of 850 L / h, and the reaction residence time is 1 h, and 1% mass concentration PAM is added to the flocculation reaction tank at a flow rate of 120 L / h, and the reaction residence time is 1 h.

[0058] After the flocculation treatment is completed, the advanced oxidation pretreatment in the present application is completed. It should be noted that in the present application, the pH of the effluent at each stage in the advanced oxidation pretreatment process is adjusted, and the pH of the effluent at each stage is selected to be within a suitable range, so that the B / C of the effluent after the advanced pretreatment process is ≥0.45.

[0059] According to the present application, subsequent biochemical treatment is performed. In the present application, the biochemical treatment includes: the flocculation effluent is subjected to EGSB anaerobic biochemical treatment and two-stage A / O biochemical treatment in sequence.

[0060] It should be noted that in the present application, the high-concentration wastewater obtained by advanced oxidation pretreatment can be mixed with low-concentration wastewater before subsequent biochemical treatment, or the high-concentration wastewater obtained by advanced oxidation pretreatment can be subjected to biochemical treatment, and the biochemical effluent can be mixed with low-concentration wastewater for subsequent treatment. There is no obvious difference between the two processes.

[0061] Therefore, in some embodiments of the present application, the flocculation effluent is continuously pumped into the EGSB anaerobic biochemical reaction tank by a water pump, the influent flow rate is 90 m 3 / h, the reaction residence time is 7 days, and 60% of COD is removed; then the EGSB anaerobic reaction effluent is introduced into a two-stage A / O biochemical treatment, the residence time is 7 days, and the two-stage A / O secondary sedimentation tank effluent removes 95% of COD. The present application does not have special restrictions on the process of EGSB anaerobic biochemical treatment and two-stage A / O biochemical treatment, and can be performed according to the process means well known to those skilled in the art.

[0062] Then subsequent advanced treatment is performed, preferably the low-concentration wastewater is pumped into the flocculation reaction sedimentation tank of the advanced process section by a pump, the influent flow rate is 1100 m 3 / h, mixed with the high-concentration wastewater treated by the EGSB and two-stage A / O process, and then the flocculation reaction sedimentation tank effluent of the advanced section is introduced into 10 columns of parallel down-in-up-out BAF biological filter tanks, a small amount of aeration is opened in each column; the BAF biological filter tank effluent is introduced into an ozone contact tank again, the ozone concentration is controlled to be 100-200 mg / L, preferably 150 mg / L, the air inlet flow rate is 200-400 Nm 3 / h, preferably 300 Nm 3 / h, the reaction residence time is 2-5 h, preferably 3 h, and after decolorization, the water is introduced into a clear water tank.

[0063] In some other embodiments of the present application, the wastewater in the low-concentration wastewater collection tank is continuously pumped into the low-concentration wastewater flotation equipment by a water pump, and is divided into 4 columns in parallel, the total flow rate of each column is controlled to be 250 m 3 / h, 10% mass concentration of PAC is added, the flow rate is 60 L / h, 1‰ mass concentration of PAM is added in the pipeline mixer of the flotation influent, the flow rate is 400 L / h, the dissolved gas pressure is about 0.5 Mpa, the flotation effluent is introduced into a comprehensive wastewater conditioning tank, and the advanced oxidation pretreatment effluent is mixed at a volume ratio of 11:1, and subsequent EGSB anaerobic biochemical reaction process and two-stage A / O biochemical treatment process are performed.

[0064] Then subsequent advanced treatment is performed, preferably the two-stage A / O biochemical effluent is introduced into 10 columns of parallel down-in-up-out BAF biological filter tanks by gravity flow, a small amount of aeration is opened in each column; the BAF biological filter tank effluent is introduced into an ozone contact tank again, the ozone concentration is controlled to be 150 mg / L, and the air inlet flow rate is 300 Nm 3 / h reaction residence time 3h, after the reaction decolorization, into the clean water pool.

[0065] The application realizes that the wastewater index is higher than the national standard A direct discharge standard by adopting advanced pretreatment technology, screening suitable process parameters, making the wastewater composition undergo physical and chemical reactions to open ring and break chain to improve the biodegradability of the wastewater, reducing the salt content of the wastewater, and making the water quality meet the environmental conditions suitable for the growth of microorganisms, and further recycling 30% of the treated and discharged wastewater, avoiding water waste, saving water resources, meeting the goals of cost saving, reducing input cost and focusing on product quality of the producers, and having wide popularization and application value as a more professional Lyocell fiber wastewater treatment technology.

[0066] It should be noted that the sludge of each flocculation reaction sedimentation tank involved above is discharged into the thickening tank, and then the sludge is conditioned and pressed into filter cake by the plate frame sludge pressing system.

[0067] In the application, the clean water is preferably subjected to magnetic coagulation and activated carbon adsorption treatment in sequence, and the effluent is recycled. In some preferred embodiments of the application, part of the clean water pool water is pumped into the magnetic coagulation and activated carbon adsorption system, and the effluent is recycled to the production cooling water system by pump lifting and backflow.

[0068] The application adopts the magnetic coagulation and activated carbon adsorption process for water recycling, and the technology does not produce concentrated water. In theory, the treated water can be recycled, but because the salt content in the wastewater is not removed, the salt content is prevented from accumulating in the production system during the recycling process, slowly affecting the salinity of the production water and the wastewater system. Therefore, according to the water consumption, 50% of the recycled water is calculated for two months, and the recycling is stopped for one month. When the water is recycled, the salt content gradually increases, and when the recycling is stopped, the water is diluted by tap water / clean water, and the salt content decreases. Through repeated operation, the salt content is finally controlled within the required concentration of the production water. Through this method, the average recycling rate of the recycled water is 33.3%.

[0069] The application also provides a lyocell fiber production wastewater treatment device, comprising:

[0070] a high-level oxidation pretreatment unit, a biochemical treatment unit and a deep treatment unit connected in sequence;

[0071] The high-level oxidation pretreatment unit comprises:

[0072] an acidic wastewater collection tank and an alkaline wastewater collection tank;

[0073] a mixed wastewater tank connected with the acidic wastewater collection tank and the alkaline wastewater collection tank;

[0074] a flotation device connected with the mixed wastewater tank;

[0075] a Fe-C micro-electrolysis acidification tank in communication with the air floatation device and the acidic wastewater collection tank;

[0076] a Fenton oxidation system in communication with the Fe-C micro-electrolysis acidification tank;

[0077] a coagulation reaction tank in communication with the Fenton oxidation system and the alkaline wastewater collection tank;

[0078] a first flocculation reaction tank in communication with the coagulation reaction tank;

[0079] the biochemical treatment unit comprises:

[0080] an EGSB anaerobic biochemical system in communication with the flocculation reaction tank;

[0081] a two-stage A / O biochemical system in communication with the EGSB anaerobic biochemical system;

[0082] the advanced treatment unit comprises:

[0083] a second flocculation reaction tank in communication with the two-stage A / O biochemical system;

[0084] a BAF biological filter in communication with the second flocculation reaction tank;

[0085] an ozone contact tank in communication with the BAF biological filter;

[0086] and a clear water tank in communication with the ozone contact tank.

[0087] In some preferred embodiments of the present application, the treatment device further comprises a magnetic coagulation tank in communication with the clear water tank, and an activated carbon adsorption tank in communication with the magnetic coagulation tank.

[0088] In order to further illustrate the present application, the following examples are provided in detail. The lyocell production collected wastewater used in the following examples of the present application is provided by the solvent recovery workshop of Sartex (Changzhou) Fibre Co., Ltd.

[0089] The raw water quality of the lyocell production collected wastewater involved in the following examples is shown in Table 1 and Table 2 as follows:

[0090] Table 1

[0091]

[0092] Table 2

[0093]

[0094] Example 1

[0095] A. The wastewater collected from the production of Lyocell is separately classified and sent to the high-concentration acid wastewater collection tank and the high-concentration alkali wastewater collection tank.

[0096] B. Use a water pump to continuously pump the wastewater from the high-concentration acid waste collection tank into the high-concentration equalization tank, with an influent flow rate of 20m³ / h. 3 At the same time, a water pump continuously sends wastewater from the high-concentration alkaline waste collection tank into the high-concentration equalization tank, with an influent flow rate of 60 m³ / h. 3 / h, allowing the two high-concentration wastewaters to be mixed in a stable ratio, can maintain the stability of wastewater quality. After the acid-base reaction of the wastewater in the high-concentration equalization tank is complete, the pH of the wastewater is controlled at approximately 9.

[0097] C. A water pump is used to continuously pump the wastewater from the high-concentration equalization tank into the pressurized dissolved air flotation equipment, with an influent flow rate of 120 m³ / h. 3 First, add 5% PAC (5% mass concentration) to the mixer in the flotation inlet pipe at a flow rate of 900 L / h. Then, add 1‰ PAM (1‰ mass concentration) to the mixer in the flotation inlet pipe at a flow rate of 150 L / h. Adjust the dissolved air pressure to approximately 0.56 MPa. The reaction residence time is 2 hours. The flotation effluent flows by gravity into the iron-carbon micro-electrolysis acidification tank.

[0098] D. Use a water pump to pump the wastewater from the high-concentration acid waste collection tank into the iron-carbon micro-electrolysis acidification tank at a flow rate of 7m³ / h. 3 / h, with 30m 3 The air flotation effluent is thoroughly mixed, at which point the pH is approximately 2.8. The mixed wastewater then flows by gravity into the iron-carbon micro-electrolysis reactor, where the reaction time is 6 hours. The micro-electrolysis reactor is supplemented with aeration using an aeration system, and the aeration is controlled to produce a small number of bubbles on the surface of the micro-electrolysis reactor.

[0099] E. The pH of the wastewater effluent after micro-electrolysis is approximately 4, and it is treated at 30m... 3 The flow rate is 1200 L / h. The ferrous sulfate solution with a mass concentration of 10% is added to the Fenton dosing tank at a flow rate of 1200 L / h. Then, hydrogen peroxide with a mass concentration of 27% is added to the Fenton reaction tank at a flow rate of 600 L / h. The reaction residence time is 3 hours.

[0100] F. The effluent from the Fenton oxidation system flows by gravity into the coagulation reaction tank, where a 3m³ pump is used to pump the effluent. 3 High-concentration alkaline wastewater is continuously pumped into the coagulation reactor and mixed with 30m³ of water. 3 Mix Fenton effluent at a flow rate of 850 L / h with the flow rate of the regulating valve to bring the pH of the coagulation reaction tank to 7.5. Then add 10% PAC to the coagulation reaction tank at a flow rate of 850 L / h and a reaction retention time of 1 h. Then add 1‰ PAM to the flocculation reaction tank at a flow rate of 120 L / h and a reaction retention time of 1 h.

[0101] G, the effluent after coagulation reaction enters the preliminary treatment process primary sedimentation tank for mud-water separation; the supernatant is discharged into the comprehensive wastewater conditioning tank, and the sludge at the bottom is discharged into the physicochemical sludge concentration tank by a sludge pump; the high-concentration wastewater pretreatment process is completed.

[0102] After the treatment of Example 1, the water quality indexes of the supernatant obtained are shown in Table 3 as follows:

[0103] Table 3

[0104]

[0105]

[0106] Example 2

[0107] A, use a water pump to continuously pump the high-concentration wastewater pretreated by advanced oxidation into the subsequent EGSB anaerobic biochemical reaction process, the influent flow rate is 90 m 3 / h, the reaction residence time is 7 days, and 60% of COD is removed;

[0108] B, the effluent after EGSB anaerobic reaction enters two-stage A / O biochemical treatment, the residence time is 7 days, and the effluent from the two-stage A / O secondary sedimentation tank removes 95% of COD;

[0109] C, use a pump to pump the low-concentration wastewater into the flocculation reaction sedimentation tank in the depth process section, the influent flow rate is 1100 m 3 / h, and the high-concentration wastewater treated by the EGSB and two-stage A / O processes is mixed;

[0110] D, the effluent from the final sedimentation tank flows into 10 columns of parallel upflow-downflow BAF biological filter tanks, a small amount of aeration is started in each column;

[0111] E, the effluent after the BAF biological filter tank enters an ozone contact tank again, the ozone concentration is controlled at 150 mg / L, the air inlet flow rate is 300 Nm 3 / h, the reaction residence time is 3 h, and the effluent after decolorization enters a clear water tank;

[0112] F, the sludge from each stage of the sedimentation tank is discharged into a concentration tank, and then enters a plate-frame sludge pressing system for pressing into filter cake after sludge conditioning;

[0113] G, use a pump to pump part of the water in the clear water tank into a magnetic coagulation and activated carbon adsorption system, and the effluent is pumped back to a production cleaning and cooling raw water collection tank for reuse.

[0114] The water quality indexes in the clear water tank after the treatment of Example 2 are shown in Table 4 as follows:

[0115] Table 4

[0116]

[0117]

[0118] Example 3

[0119] A, using water pump to send the sewage of high concentration acid waste collection pool into high concentration adjusting pool continuously, the inflow is 20m 3 / h, and using water pump to send the sewage of high concentration alkali waste collection pool into high concentration adjusting pool continuously, the inflow is 60m 3 / h, so that the two kinds of high concentration waste water are mixed in stable proportion, the waste water quality can be kept stable, and when the reaction of the waste water in high concentration adjusting pool is completed, the pH of the waste water is controlled to be about 9;

[0120] B, using water pump to send the waste water in high concentration adjusting pool into pressurized dissolved air flotation equipment continuously, the inflow is 120m 3 / h, 5% mass concentration PAC is added into the dosing pipe mixer of the air flotation inflow pipeline, the flow is 900L / h, 1‰ mass concentration PAM is added into the pipeline mixer of the air flotation inflow, the flow is 150L / h, and the dissolved air pressure is adjusted to be about 0.56Mpa; the reaction residence time is 2h, and the air flotation effluent flows into the iron-carbon micro electrolysis acidification pool;

[0121] C, using water pump to send the waste water in high concentration acid waste collection pool into the iron-carbon micro electrolysis acidification pool, the flow is 7m 3 / h, and the air flotation effluent of 30m 3 / h is fully mixed, at this time, the pH is about 2.8, the mixed waste water flows into the iron-carbon micro electrolysis reaction pool, the reaction residence time is 6h; the micro electrolysis pool uses aeration system to supplement aeration, and a small amount of bubbles is generated on the surface of the micro electrolysis pool by controlling the aeration;

[0122] D, the pH of the waste water after the micro electrolysis is about 4, and the flow is 30m 3 / h, and the waste water flows into the Fenton oxidation reaction system again, 10% mass concentration ferrous sulfate solution is added into the Fenton dosing pool, the flow is 1200L / h, 27% mass concentration hydrogen peroxide is added into the Fenton reaction pool, the flow is 600L / h, and the reaction residence time is 3h;

[0123] E, the effluent after the Fenton reaction flows into the coagulation reaction pool, 3m 3 / h high concentration alkali waste is continuously sent into the coagulation reaction pool by using water pump, and the flow is 30m 3 / h Fenton effluent is mixed, the opening degree of the regulating valve is controlled, so that the pH of the coagulation reaction pool is about 7.5; 10% mass concentration PAC is added into the coagulationInternal reaction pool, the flow is 850L / h, the reaction residence time is 1h, and 1‰ mass concentration PAM is added into the flocculation reaction pool, the flow is 120L / h, and the reaction residence time is 1h;

[0124] F, the low concentration wastewater collected in the low concentration wastewater collection tank is continuously pumped into the low concentration wastewater flotation equipment by a water pump, and is divided into 4 parallel columns, each column controls a total flow of 250 m 3 / h, 10% mass concentration of PAC is added at a flow rate of 60 L / h, 1‰ mass concentration of PAM is added in the pipeline mixer of the flotation inlet water at a flow rate of 400 L / h, the dissolved gas pressure is about 0.5 Mpa, the flotation outlet water is mixed with the advanced oxidation pretreatment outlet water at a volume ratio of 11:1 in the comprehensive wastewater conditioning tank, and subsequent EGSB anaerobic biochemical reaction process is carried out;

[0125] G, the wastewater in the comprehensive wastewater conditioning tank is continuously pumped into 5 columns of parallel EGSB anaerobic process sections by a water pump, the inlet flow rate of each column is 250 m 3 / h, the residence time of reaction is 24 h;

[0126] H, the EGSB anaerobic reaction outlet water enters 5 columns of parallel two-stage A / O biochemical treatment, the residence time of each column is 5 days, the dissolved oxygen in the aerobic tank is about 2 mg / L, the sludge reflux is 50%, the nitrification liquid reflux is 200%, and 90% of COD is removed in the two-stage A / O secondary sedimentation tank outlet water of the latter section;

[0127] I, the secondary sedimentation tank outlet water is self-flowing into the final sedimentation tank flocculation reaction sedimentation tank, 10% mass concentration of PAC is added at 1200 L / h, and 1‰ mass concentration of PAM is added at a flow rate of 400 L / h; the reaction residence time is 3 h, the sedimentation time in the inclined plate sedimentation tank is 6 h, the supernatant is discharged into the BAF filter tank, and the sludge is discharged into the sludge thickening tank;

[0128] J, the final sedimentation tank outlet water is self-flowing into 10 columns of parallel lower-inlet upper-outlet BAF biological filter tanks, a small amount of aeration is started in each column;

[0129] K, the BAF biological filter tank outlet water enters the ozone contact tank again, the ozone concentration is controlled at 150 mg / L, the inlet gas flow rate is 300 Nm 3 / h, the reaction residence time is 3 h, and after decolorization, the reaction enters the clear water tank;

[0130] L, after the sludge in each stage of the sedimentation tank is discharged into the thickening tank, the sludge is conditioned, pressed into filter cake by a plate-frame sludge pressing system;

[0131] M, part of the clear water tank water is pumped into a magnetic coagulation and activated carbon adsorption system, and the outlet water is pumped back to a production cleaning and cooling raw water collection tank for reuse.

[0132] The water quality indexes in the clear water tank after treatment in the embodiment 3 are shown in Table 5:

[0133] Table 5

[0134]

[0135]

[0136] In summary, the present application is directed to the special properties of Lyocell fiber industrial wastewater, the water treatment process route is newly planned, and the wastewater is classified and collected according to the properties, and the appropriate process is selected for treatment, so as to realize more sufficient adjustment and treatment of wastewater. The new process route proposed by the present application realizes that the wastewater index is higher than the national standard A direct discharge standard, and makes the treated and discharged wastewater can be further recycled by more than 30%, avoids the waste of water, saves water resources, meets the project goals of saving cost, reducing input cost and focusing on product quality of the producer, and has wide popularization and application value as a more professional Lyocell fiber sewage treatment technology.

[0137] The above description of disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating wastewater from lyocell fiber production, characterized in that, include: S1: Advanced Oxidation Pretreatment: Acidic wastewater and alkaline wastewater from lyocell fiber production are mixed and reacted to obtain a first mixed wastewater. The pH of the first mixed wastewater is controlled at 9-10, and it is subjected to air flotation treatment to obtain air flotation effluent. The acidic wastewater and the air flotation effluent are mixed to obtain a second mixed wastewater, and the pH of the second mixed wastewater is controlled at 2.8-3. The second mixed wastewater is subjected to iron-carbon micro-electrolysis treatment, and the pH of the micro-electrolysis effluent is controlled at 4-4.

5. Fenton oxidation treatment is performed to obtain Fenton oxidation effluent. The Fenton oxidation effluent is mixed with the alkaline wastewater to obtain a third mixed wastewater, and the pH of the third mixed wastewater is controlled at 7.5-9.

0. Coagulation treatment and first flocculation treatment are performed to obtain first flocculated effluent. S2: Biochemical treatment: The first flocculated effluent is subjected to EGSB anaerobic biochemical treatment and two-stage A / O biochemical treatment in sequence to obtain A / O biochemical effluent; S3: Advanced treatment: The A / O biological effluent is subjected to a second flocculation treatment, BAF treatment and ozone treatment in sequence to obtain ozone effluent, thus obtaining clean water.

2. The processing method according to claim 1, characterized in that, The air flotation treatment is carried out using 5-8 wt% PAC and 1-5 wt% PAM; The ratio of the influent flow rate, PAC flow rate, and PAM flow rate in the air flotation treatment is 120 m³ / s. 3 / h: (800~1000)L / h: (100~200)L / h; The dissolved air pressure in the air flotation treatment is 0.56–0.6 MPa; the treatment time is 1–5 hours.

3. The processing method according to claim 1 or 2, characterized in that, The iron-carbon micro-electrolysis treatment time is 4 to 8 hours.

4. The processing method according to any one of claims 1 to 3, characterized in that, The Fenton oxidation treatment is performed using a 10-15 wt% ferrous sulfate solution and 27-35 wt% hydrogen peroxide for 2-6 hours. The ratio of the influent flow rate, ferrous sulfate solution flow rate, and hydrogen peroxide flow rate for the Fenton oxidation treatment is 30 m³ / h. 3 / h: (1000~1500)L / h: (500~1000)L / h.

5. The processing method according to any one of claims 1 to 4, characterized in that, The coagulation treatment uses 10-15 wt% PAC; The first flocculation treatment was carried out using 1-5 wt‰ PAM; The ratio of the influent flow rate, PAC flow rate, and PAM flow rate for the coagulation treatment is 30 m³ / s. 3 / h: (800~1000)L / h: (100~200)L / h.

6. The processing method according to any one of claims 1 to 5, characterized in that, The residence time for the EGSB anaerobic biochemical treatment is 1 to 7 days; The residence time for the two-stage A / O biochemical treatment is 1 to 7 days.

7. The processing method according to any one of claims 1 to 6, characterized in that, The ozone concentration in the ozone treatment is 100–200 mg / L, and the inlet flow rate is 200–400 Nm³. 3 / h; The ozone treatment time is 2 to 5 hours.

8. The processing method according to any one of claims 1 to 7, characterized in that, After obtaining clean water, the process further includes sequentially subjecting the clean water to magnetic coagulation and activated carbon adsorption treatments, with the effluent being recycled.

9. A treatment device for wastewater from lyocell fiber production, characterized in that, include: The advanced oxidation pretreatment unit, the biochemical treatment unit, and the deep treatment unit are connected in sequence. The advanced oxidation pretreatment unit includes: Acidic wastewater collection tank and alkaline wastewater collection tank; A mixed wastewater tank connected to the acidic wastewater collection tank and the alkaline wastewater collection tank; An air flotation device connected to the aforementioned mixed wastewater tank; An iron-carbon micro-electrolysis acidification tank connected to the air flotation equipment and the acidic wastewater collection tank; A Fenton oxidation system connected to the iron-carbon micro-electrolysis acidification cell; A coagulation reaction tank connected to the Fenton oxidation system and the alkaline wastewater collection tank; A first flocculation reaction tank connected to the coagulation reaction tank; The biochemical processing unit includes: An EGSB anaerobic biological system connected to the first flocculation reaction tank; A two-stage A / O biochemical system is connected to the EGSB anaerobic biochemical system; The depth processing unit includes: The second flocculation reaction tank is connected to the two-stage A / O biochemical system; BAF biological filter connected to the second flocculation reaction tank; An ozone contact tank connected to the BAF biological filter; And a clear water tank connected to the ozone contact tank.

10. The processing apparatus according to claim 9, characterized in that, The treatment device also includes a magnetic coagulation tank connected to the clear water tank, and an activated carbon adsorption tank connected to the magnetic coagulation tank.

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